GCSB protesters have laid formal complaints with the Broadcasting Standards Authority after an inaccurate television report said rocks and bottles were thrown during a Palmerston North rally.

A 3 News report on Saturday claimed Palmerston North people clashed with police, throwing bottles and rocks, during the city's protest.

Police have refuted these claims and 3 News has accepted it was an error, and will issue an apology in tonight's news bulletin.

Palmerston North people were among the thousands nationwide making a public stand to oppose the Government's Communications Security Bureau Amendment Bill - which will expand the legal power of the GCSB to spy on New Zealanders.

About 150 people gathered in the city centre to march around The Square and voice their opinions on the controversial topic of covert surveillance.

Protest organiser Teanau Tuiono said the event was a family-friendly, peaceful protest that allowed people to be informed on the proposed law change. The organisers invited protesters to the pub afterward to continue talks.

Tuiono said he was disappointed when he saw the opening segment of TV3's 6pm news bulletin stating Palmerston North protesters had been causing havoc, but with no footage of them doing so.

''It inferred we were violent towards police and there were no such incidents.

''The reporting of these fictitious actions are inaccurate and denigrates the support in the provinces ... and it begs the question, why would they do it?''

Protesters said they had laid complaints with 3 News, MediaWorks, which owns TV3, and the Broadcasting Standards Authority.

''It casts Palmerston North in a bad light, and it was untrue and inaccurate,'' Tuiono said.

''A significant portion of the population is going to tune into TV3 news and say 'Hey, look they're up to trouble in Palmerston North' and they'll believe it.

''The intention was to support what was happening around the country in a display of solidarity.''

TV3's Auckland bureau chief Keith Slater said an email from a person within the Palmerston North area provided the tip.

He would not comment on why it wasn't verified.

''3 News acted on information provided that was incorrect and we will rectify that error,'' he said before the apology went to air.

Palmerston North Sergeant Gina Atkinson, who attended the protest, said it was peaceful and no objects were thrown.

Police weren't asked to attend but because it was in her patrol area, Atkinson went along.

She said organisers did everything correctly by contacting the police and the council beforehand. No complaints were received afterwards.